Healthy children may cough ~10 times/day
Viral respiratory tract infection may cause self-limited post-viral cough, acute bronchitis, or laryngotracheitis (croup)
- 35-40% still cough 10 days after onset of common cold (school-age), 10% at 25 days (pre-school)
- Recurrent viral respiratory infections may appear as persistent cough

Abnormal cough

Specific cough
- Sign/symptoms of an underlying respiratory or systemic disease are present
- Usually a wet cough; chronic wet cough (with or without production of purulent sputum) is always pathologic and warrants investigations for a persistent infection, foreign body, or immunodeficiency
- Common
  - UACS (upper airway cough syndrome) - post nasal drip accompanying rhinitis/sinusitis
    - Post-viral respiratory infection
    - Bacterial sinusitis
    - Allergic and non-allergic rhinitis
    - Allergic fungal sinusitis
  - Asthma
  - Protracted/persistent bacterial bronchitis (PBB) - defined as more than 4 weeks of wet cough (somtimes non-specific noisy breathing and wheezing) that responds to antibiotic treatment
    - Frequent cause in children <7 yo, associated with laryngo/tracheo/bronchomalacia in children <3 yo, age of onset is often <1 yo; children otherwise have normal growth/development and are afebrile
    - BAL typically demonstrates neutrophilia, and commonly S. pneumoniae, H. influenzae, M. catarrhalis, S. aureus; malacia may interfere with normal clearance of mucus which predisposes to infection
    - Resolution with antibiotics (e.g. Augmentin or 2nd/3rd generation cephalosporin x 10 days-6 weeks, relapse frequent with shorter courses), may progress to chronic suppurative lung disease and bronchiectasis if untreated
  - Atypical bacterial pneumonia
    - B. pertussis
      - Paroxysmal spasms of cough, often with inspiratory whoop, post-tussive emesis, and substantial interference with sleep, but characteristic cough may not be seen in previously immunized older children; bacteria cleared by 4 weeks but cough may persist for weeks afterward
      - Macrolide antibiotics eliminate infectiousness but do not change clinical course
      - Consider in any child with chronic cough <3 months ("100 days") even if immunized
    - B. parapertussis - similar presentation as pertussis except less severe, pertussis vaccination not protective.
    - Mycoplasma, Chlamydia
  - Foreign body - Cough with acute onset after choking episode, CXR may be normal in 20-40%; obtain inspiratory and expiratory CXR and/or frontal and right and left lateral decubitus films
  - GERD - Controversial whether a common cause except in conditions predisposing to aspiration
    - Cough itself may elicit reflux
  - Habit cough (psychogenic cough, cough tic) - Harsh, dry, often honking or barky repetitive cough occurring intermittently throughout the day, often with great frequency, child is usually indifferent (belle indifference), with significant improvement with distraction and complete absence when asleep (but may interfere with falling asleep)
    - A variation of habit cough may be chronic throat clearing
- Less common
  - Bronchiectasis/recurrent pneumonia - Chronic suppurative lung disease (CSLD), CF, ciliary dyskinesia, ABPA, immunodeficiency, congenital lung lesions, foreign body, fistula
    - Primary ciliary dyskinesia is rare (1 in 15,000 births) and should be considered only when a persistent cough is present virtually from birth, generally in association with chronic otitis media; 50% have situs inversus (Kartagener syndrome)
  - Aspiration - Swallowing dysfunction, neuromuscular disease, laryngeal abnormality, tonsil/adenoid hypertrophy, fistula, severe GERD
    - Achalasia - predisposes to aspiration, and dilated esophagus may compress trachea
  - Chronic or less common infections - TB, fungi, parasites, etc.
  - Interstitial lung disease - Rheumatic disease, drugs, radiation, etc.
  - Airway structural abnormality - Laryngo/tracheo/bronchomalacia, tumors, tonsils/uvula touching epiglottis, vascular ring, etc.
  - Cardiac disease - Pulmonary hypertension, pulmonary edema, etc.
Non-specific cough- Cough is sole or predominant symptoms (other signs/symptom absent), usually dry
- Postinfectious (post-viral) cough - Typically related to viral infection and increased cough receptor sensitivity; resolves spontaneously
- Cough nerve reflex - Stimulation of the auricular branch of the vagus nerve or the posterior-inferior wall of the external acoustic meatus (e.g. foreign body, hair touching tympanic membrane, wax in ear)
- Atopic cough - Isolated, dry/non-productive, bronchodilator resistant cough with allergic sensitization, eosinophilic tracheobronchitis, and airway cough receptor hypersensitivity that does not progress to asthma; treated with ICS.

Final diagnosis in a study of 108 children (1-7 yo, median 2.6 yo) with chronic cough (Marchant):
- 40% - PBB
- 22% - natural resolution
- 6% - bronchiectasis, on HRCT of chest
- 5% - aspiration disorder
- 4% - asthma, episodic wheezers with responsiveness to albuterol and ICS
- 4% - eosinophilic bronchitis (sputum eosinophilia) or hypereosinophilic syndrome
- 3% - post nasal drip (UACS)
- 3% - GERD, diagnosis via pH probe or characteristic biopsy, responsive to medical therapy
- Rest (<2%) - habit cough, bronchiolitis obliterans, TB, Pertussis, Mycoplasma infection

Diagnosis

History and Physical

"Specific cough pointers" are signs/symptoms suggesting that cough is due to an underlying respiratory or systemic disease.

Indicators of specific cough in children based on H&P:
- Daily, wet, or productive cough
- Auscultatory findings (wheeze or crackles)
- Chronic dyspnea
- Exertional dyspnea
- Hemoptysis
- Duration >6 months
- Recurrent pneumonia
- Cardiac abnormalities (including murmurs)
- Immune deficiency
- Failure to thrive
- Digital clubbing
- Swallowing problems

Is there a family history of respiratory disorders and atopy?
What medications is the child on, what treatments has the child had for the cough and what effect have they had on the cough frequency and severity?
Does the cough disappear when asleep (suggests psychogenic or habit cough)?
Does the child smoke cigarettes or exposed to environmental smoke?

Testing for GI causes of cough

Upper GI series - NOT a useful test for reflux (sensitivity 31-86%), only looking for plumbing problems such as malrotation or tracheoesophageal fistula
GE scan/milk scan - NOT useful for reflux (sensitivity 15-59%), OK for aspiration, OK for delays in gastric emptying
Endoscopy - earlier studies suggest 95% sensitivity. In age of PPI, may be lower, crucial to make diagnosis of eosinophilic esophagitis which can present with cough
PPI trial - sensitivity 78-95%
Impedance probe - sensitivity 75-85%
Modified barium swallow - NOT for reflux, only for aspiration or abnormalities of the upper esophagus
Other tests: motility testing (achalasia), BRAVO, cough catheter (impedance with pressure sensors), reflux breath testing, restech (probe in posterior pharynx)

Management Algorithms

Chang CHEST Guideline (2006)

Figure 3

Chang Clinical Trial (2010)

Chipps (Simplified Chang Algorithm)

Figure 2

Rank Simplified Algorithm

Marchant Study Algorithm

Modified BTS Guideline

Treatment

OTC cough medications (including medications with dextremethorphan and codeine) not recommended for children <6 years old (AAP)
Honey up to 2 teaspoons (10 mL) qhs found to be superior to dextremethorphan and placebo for nocturnal cough
Specific etiology-based treatment if possible
Multiple etiologies may need to be treated concomitantly